The present invention relates to a linear actuator with a shock-absorbing mechanism for causing a slide table for carrying a workpiece to linearly reciprocate by a driving mechanism and for stopping the slide table at stroke ends in shock-absorbed manner.
Conventionally, in this type of linear actuator with a shock-absorbing mechanism, a guide rail 3 extending in a longitudinal direction and a rodless cylinder 4 in parallel to the guide rail 3 are disposed on a rectangular rail base 1 as shown in FIG. 4. End walls 2 and 2 of a pair disposed on opposite end sides of the guide rail 3 and also functioning as end covers of opposite end portions of the rodless cylinder 4 are provided to longitudinal opposite end portions of the rail base 1. A slide table 5 for carrying a workpiece is provided onto the guide rail 3 to be driven by the rodless cylinder 4 to linearly reciprocate.
Ports 8 for supplying fluid pressure to the rodless cylinder 4 are provided to the end walls 2 and two shock absorbers 6 and 6 are mounted respectively through support blocks 7 to inner sides of the two end walls 2 to face opposite end faces of the slide table 5.
In such a linear actuator, if the fluid pressure is supplied to the rodless cylinder 4, the slide table 5 is driven by the rodless cylinder 4 to move on the guide rail 3, the end face of the slide table 5 collides with a push rod 6a for expanding and contracting of the shock absorber 6 at each stroke end, and the slide table 5 stops in a shock-absorbed manner.
However, in such a prior-art linear actuator, the two shock absorbers 6 and 6 are disposed on the inner sides of the end walls 2 and 2 to project toward the slide table 5 and the slide table 5 reciprocates between the shock absorbers and stops at each the stroke end in a state in which the push rod 6a is contracted. Therefore, a stroke of the slide table 5 is short in spite of a large entire length of the apparatus.
Moreover, it is difficult to discharge dust or the like which has sett led on the rail base 1 and the guide rail 3 because of the end walls 2 and 2 and maintainability is poor.
Therefore, there is one disclosed in Japanese Patent No. 3011084 in which stoppers are provided in positions at inward distances from end faces of the slide table under the slide table and a part of the shock absorber enters the slide table at each stroke end of the slide table.
However, because the two shock absorbers and the two stoppers are disposed coaxially in this example, positions of them interfere with each other and a depth of each the space portion where the shock absorber enters cannot be set to be very large depending on a size of the slide table. Therefore, the stroke of the slide table cannot be set to be large in spite of a length of the apparatus. Moreover, because the rail base has end walls at opposite sides of the rail base, the poor main tainability is not improved.
It is an object of the present invention to provide a small-sized linear actuator with a shock-absorbing mechanism in which a plurality of shock absorbers and a plurality of stoppers are disposed in rational positions with respect to each other to thereby upsize a stroke of a slide table and to improve maintainability.
To achieve the above object, according to the invention, there is provided a linear actuator with a shock-absorbing mechanism, the actuator comprising: a rail base with open opposite ends without end walls standing upward from axial opposite end portions; a guide rail provided in an axial direction on the rail base; a slide table disposed on the rail base to linearly reciprocate along the guide rail; a driving mechanism for driving the slide table; a plurality of shock absorbers disposed in parallel to each other in different positions on the left and right in the slide table with push rods for expanding and contracting projecting outside from opposite end faces of the slide table in a moving direction of the slide table; and a plurality of stoppers which are disposed at the opposite end portions of the rail base to face the respective shock absorbers and with which the respective push rods collide at stroke ends of the slide table.
In the linear actuator of the invention having the above structure, the shock absorbers are mounted to the slide table such that only the push rods project outside from the opposite end faces, it is possible to substantially shorten an entire length of the linear actuator to downsize the actuator and it is possible to upsize an operating stroke as compared with a case in which the entire shock absorbers are mounted to project from the opposite end faces of the slide table. Moreover, because the two shock absorbers are disposed in parallel to each other in the different positions on the left and right in the slide table, the shock absorbers do not conflict with each other for the position and do not obstruct shortening of the slide table unlike a case in which the shock absorbers are disposed coaxially.
Because end walls are not provided to the opposite end portions of the rail base and the opposite ends are open, it is possible to easily discharge dust or the like which has settled on the rail base and the guide rail through the open opposite end portions and maintainability is improved.
In the invention, it is preferable that each the stopper is formed of a support block mounted onto the rail base and a collision face provided to the support block and that a position of at least one of the support block and the collision face is adjustable in the moving direction of the slide table.
According to the invention, there is provided a linear actuator with a shock-absorbing mechanism, the actuator comprising a plurality of shock absorbers mounted to support blocks disposed in different positions on the left and right of the opposite end portions of the rail base with push rods for expanding and contracting oriented in such directions as to face each other and stoppers formed in different positions on the left and right in the slide table and at such distances from opposite end faces of the slide table in a moving direction of the slide table that at least the shock absorbers out of the shock absorbers and the support blocks can enter the slide table, the push rods of the shock absorbers colliding with the stoppers at stroke ends of the slide table.
In a preferred embodiment of the invention, the driving mechanism is detachably mounted to one of side portions of the rail base and has an outside moving member driven to reciprocate in the axial direction of the rail base and the moving member and the slide table are detachably engaged with each other.
The guide rail is provided to a central portion of the rail base and the plurality of shock absorbers and the plurality of stoppers are provided to the slide table and the rail base in positions on opposite sides of the guide rail.